Nonionic Cellulose Ether Research Articles

Re-characterization of the surface properties of non-ionic cellulose ethers by means of column wicking technique

Re-characterization of the surface properties of non-ionic cellulose ethers by means of column wicking technique

Sustained release of acetaminophen from a heterogeneous mixture of two hydrophilic non-ionic cellulose ether polymers

This study examined the release of acetaminophen (APAP) from hydroxypropyl methylcellulose (HPMC) and hydroxypropyl cellulose (HPC) matrices. The effect of pseudoephedrine (PE) as a co-active, HPMC:HPC ratio, polymer loading, pH of the dissolution media, and compression force on APAP release were studied. Granules formulated with APAP or both APAP and PE, and various blends of HPMC and HPC were compressed into tablets at different compression forces. APAP release from the matrix tablets was not considerably influenced by changes in HPMC:HPC ratio or compression force. The rate of drug release was significantly affected by pH of the dissolution media, total polymer loading, and the presence of PE. Drug release from the formulations containing both APAP and PE was slower than those containing only APAP. Drug release from tablets formulated with APAP only showed an initial burst at pH 1.16 or 7.45. Formulations containing both APAP and PE showed slower drug release at pH 1.16 than at pH 7.4. The drug release data showed a good fit to the Power Law Model. The mechanism of drug release is consistent with a complex behavior. The results of the tablet erosion studies indicated that the amount of APAP released was linearly related to the percentage of tablet weight loss. The kinetics of tablet water uptake was consistent with a diffusion and stress relaxation mechanism.

Chemical structure and glass transition temperature of non-ionic cellulose ethers

Glass transitions of several non-ionic cellulose ethers differing in molecular mass and nature and amount of substituents were analyzed (as compressed probes) by differential scanning calorimetry (DSC), modulated temperature differential scanning calorimetry (TMDSC@®), and oscillatory rheometry. In general, the low energy transitions accompanying the Tg of methylcellulose (MC), hydroxypropyl methylcellulose (HPMC), and hydroxypropylcelluloses of low (L-HPC) or medium-high (HPC) degree of substitution were difficult to characterize using DSC. Non-reversing heat flow signals obtained in TMDSC experiments were more sensitive. However, the best resolution was obtained using oscillatory rheometry since these cellulose ethers undergo considerable changes in their storage and loss moduli when reaching the Tg. Oscillatory rheometry also appears as a useful technique to characterize the viscoelastic behavior and thermal stability of pharmaceutical tablets. Tg values followed the order HPC (105°C)<HPMC (170-198°C)<MC (184-197°C)<L-HPC (220°C). For HPMCs, the Tg increases as the methoxyl/hydroxypropoxyl content ratio decreases. The results indicate that Tg depends strongly on the structure of the cellulose ethers. In general, increasing the degree of substitution of cellulosic hydroxyls, the hydrogen bonding network of cellulose decreases (especially when the substituents cannot form hydrogen bonds) and, in consequence, Tg also decreases.

Comparative evaluation of rate of hydration and matrix erosion of HEC and HPC and study of drug release from their matrices

Hydrophilic polymers, in contact with the dissolution medium, may swell and make a continuous gel layer, erode or undergo combination of the two. The swelling action of these polymers is controlled by the rate of their hydration in the dissolution medium. The extent of polymer swelling, relative mobilities of dissolution medium and drug, and matrix erosion dictate the kinetics as well as mechanism of drug release from the polymeric matrices. The objective of the present investigations was to study the rate of hydration and the rate of matrix erosion of two hydrophilic, non-ionic cellulose ethers, i.e., hydroxyethylcellulose (HEC) and hydroxypropylcellulose (HPC), and to compare the kinetics and mechanism of drug release from their matrices. Chlorpheniramine maleate was used as the model drug. Matrix tablets containing chlorpheniramine maleate, HEC or HPC and dicalcium phosphate were compressed at 156 MPa pressure. The rate of hydration of the polymer, rate of erosion of the matrices and in vitro drug release studies were carried out in phosphate buffer (pH 7.4). The hydration studies of the two polymers demonstrated that due to relatively larger water uptake, the degree of swelling of HEC matrices was considerably higher as compared to the HPC matrices. Also, HEC matrices exhibited relatively higher erosion as compared to HPC matrices. The drug release from HEC matrices occurred by non-Fickian transport, i.e., combination of drug diffusion and polymer swelling, while drug release from HPC matrices was controlled primarily by diffusion through pores and channels in the structure. The t 50%, time to reach 50% drug release, for HEC matrices was 4.8 h and that for HPC matrices was 6.5 h which indicates that a higher polymer level was needed in the case of HEC matrices to sustain the drug release for up to 12 h of dissolution as compared to HPC matrices due to relatively higher hydrophilicity of HEC.

Nonionic Cellulose Ethers as Potential Drug Delivery Systems for Periodontal Anesthesia

Nonionic cellulose ethers displaying a lower consolute temperature, or cloud-point, close to body temperature were investigated as potential carrier systems for the delivery of local anesthetic agents to the periodontal pocket. The interaction between the polymers, i.e., ethyl(hydroxyethyl)cellulose (EHEC) and hydrophobically modified EHEC (HM-EHEC), and ionic surfactants was determined in the absence and in the presence of the local anesthetic agents lidocaine and prilocaine. The cloud-point and rheology data indicate interactions between the polymer and both anionic and cationic surfactants. More precisely, a number of ionic surfactants were found to result in an increase in cloud-point at higher surfactant concentrations, a surfactant-concentration-dependent thickening, and a temperature-induced gelation upon heating. Upon addition of the local anesthetic agents lidocaine and prilocaine in their uncharged form to EHEC and HM-EHEC, in the absence of surfactants, only minor interaction with the polymer could be inferred. However, these substances were found to affect the polymer–surfactant interaction. In particular, the drug release rate in vitro as well as the stability and temperature-dependent viscosity were followed for an EHEC/SDS system and EHEC/myristoylcholine bromide system upon addition of lidocaine and prilocaine. The data indicate a possibility of formulating a local anesthetic drug delivery system suitable for administration into the periodontal pocket where at least small amounts of active ingredients can be incorporated into the system without severely affecting the gelation behavior. The results found for the cationic myristoylcholine bromide system are particularly interesting for the application in focus here since this surfactant is antibacterial and readily biodegradable.

セルロースエーテルを添加したコンクリートの材料分離特性に関する材料設計法

The nonionic cellulose ether, a kind of water-soluble polymer, is used for several cement matrices such as plastering mortar, ceramic tile mortar, self smoothing flooring compound, high fluidity concrete, antiwashout underwater concrete, shot concrete and cement extrusion molding e. t. c.. The purpose of this study was to clarify the influence of the moIecuIar weight and the concentration of cellulose ether on characteristic in three kind of concrete (high fluidity concrete, antiwashout underwater concrete and shot concrete) containing cellulose ether. The results obtained were as follows. 1) Characteristics of concrete (such as the resistance of segregation e. t. c.), as well as mortar and cement paste was previously reported, were affected by the molecular weight and the concentration of cellulose ether. 2) Characteristic factors were able to be expressed by the following function of the molecular weight and the oncentration on material design method. Characteristic factors ∝ M^α×C^β where M : moIecuIar weight of cellulose ether, C : concentration, α, β : (0.67, 1.0) or (-0.67, -1.0)

Association in nonionic cellulose ether solutions due to microcrystallites?

Cellulose derivatives have a strong tendency to associate in solution and at interfaces and this underlies many applications. Nonionic cellulose ethers are often of the clouding type, i.e. they phase separate at higher temperatures due to a worsening of the solvency conditions. The association due to the presence of more or less strongly hydrophobic groups and due to solvency conditions in general leads to important rheological effects and gives the basis for uses as associative thickeners. This association is short-lived and reversible and has been extensively investigated. In this report we suggest, based on different recent observations for solutions of ethyl(hydroxyethyl)cellulose (EHEC), that there are also very long-lived associations formed and we suggest that this can be referred to structures similar to those in the crystalline state of cellulose. This association due to ‘microcrystallites’ is strongly dependent on the distribution of substituents along the polymer chain. It is strongly promoted by ‘blockiness’, i.e. by an inhomogeneous substitution pattern of hydroxyethyl and ethyl groups along the polymer chains in a way such that unsubstituted parts are separated by more substituted regions. We suggest that the unsubstituted parts of the EHEC chains are likely to be strongly associated for the same reasons as native cellulose, which is insoluble in water, is arranged in crystalline arrays. The presence of crystallinity has been indicated by measuring X-ray diffraction on a sample (very) concentrated in EHEC (20 wt.%). In agreement with the packing distance in native cellulose, a diffuse ring corresponding to 7.0–13.5 Å was observed.

Thermodynamics of Interaction between Some Cellulose Ethers and SDS by Titration Microcalorimetry: II. Effect of Polymer Hydrophobicity

A titration calorimetric study of the interaction between nonionic cellulose ethers and ionic surfactant (SDS) has been extended to a larger number of polymers to explore the effect of variation of polymer hydrophobicity on the energetics of the process. “Hydrophobicity” as used here is an overall effect of the nature, degree, and number of substituents and is characterized by the cloud point and (aqueous) surface tension lowering abilities of the polymer. A direct correlation is found between the extent of “hydrophobicity” and the endo-enthalpic peak in the initial SDS concentration region of interaction. However, the overall mechanism of interaction is similar for all the polymers, being dominated by polymer–surfactant interactions initially and converting into a surfactant–surfactant interaction process at higher SDS concentrations. The importance of polymer characteristics thus becomes weaker at the later stages of the process. Differences between the polymers is also reduced by an increase of temperature, leading to a near overlap of observed enthalpy curves at 40°C. The energetics of interaction are also mirrored by the isothermal surfactant binding curves and the changes in macroscopic and microviscosity of the system.

Thermodynamics of Interaction between Some Cellulose Ethers and SDS by Titration Microcalorimetry: I. EHEC and HPMC

The interaction between certain nonionic cellulose ethers (ethyl hydroxyethyl cellulose and hydroxypropyl methyl cellulose) and sodium dodecyl sulphate (SDS) has been investigated using isothermal titration microcalorimetry at temperatures between 25–50°C. The observed heat flow curves have been interpreted in terms of a plausible mechanism of the interaction of the substituent groups with SDS monomers and clusters. The data have been related to changes occuring in the system at the macro- and microscopic levels with the addition of surfactants and with temperature. The process consists predominantly of polymer–surfactant interactions initially and surfactant–surfactant interactions at the later stages. A phenomenological model of the cooperative interaction (adsorption) process has been derived, and earlier published equilibrium binding data have been used to recover binding constants and Gibbs energy changes for this process. The adsorption enthalpies and entropies have been recovered along with the heat capacity change. The enthalpic cost of confining the nonpolar regions of the polymers in surfactant clusters is high, but the entropy gain from release of hydration shell water molecules as well as increased freedom of movement of these nonpolar regions in the clusters gives the process a strong entropic driving force. The process is entropy-driven initially and converts to being both enthalpy and entropy-driven at high SDS concentrations. An enthalpy–entropy compensation behavior is seen. Strongly negative heat capacity changes have been obtained resulting from the transfer of nonpolar groups from aqueous into nonpolar environments, as well as a reduction of conformational domains that the chains can populate. Changes in these two components cause the heat capacity change to become less negative at the higher binding levels. The system can be classified as exhibiting nonclassical hydrophobic binding at the later stages of binding.

Phase separation induced by dilution in a system of a hydrophobically modified polymer

A phase map of a nonionic cellulose ether, and an anionic surfactant (SDS), in aqueous solution has been determined. The influence of hydrophobic modification of the polymer has been investigated. In the system containing the hydrophobically modified polymer, a phase separation is induced by dilution. We suggest that the mechanism is related to a ‘bridging flocculation’. The polymer concentration in the polymer rich bottom phase is determined by association strength, preferred distance between the ‘tie points’, and, in the case of charged surfactant, electrostatic swelling. At higher surfactant concentrations the two polymer systems behave similar, and the effect of hydrophobic modification is lost.

Influence of a cellulosic ether carrier on the structure of biphasic calcium phosphate ceramic particles in an injectable composite material

An injectable composite material based on biphasic calcium phosphate (BCP) and a nonionic cellulose ether has been elaborated for use in percutaneous surgery for spine fusion. This paper reports the characterization results of this material by spectroscopic techniques including X-ray diffraction (XRD), infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) fitted with an energy dispersive X-Ray analysis system and high-resolution transmission electron microscopy (HR-TEM). From FTIR and XPS results, it was observed that the adhesion between the polymer and the ceramic might be insured by oxygen bridging developed through an ionic bonding between calcium ions and (C;O) groups of the polymer. Moreover, XPS showed attraction of Ca 2+ ions in the polymer matrix, while the ceramic surface was modified in a HPO 2- 4-rich layer. These results suggest a possible dissolution/precipitation process at the interface ceramic/polymer. HR-TEM observations supported this hypothesis, showing a light contrasted fringe at the surface of the ceramic grains in the composite paste. As well, changes in the XRD spectra could indicate a small decrease in the crystal size of the BCP powder through the contact to polymer solution. In addition, SEM observation showed a decrease of the initial BCP granulometry. Aggregates of 80–200 μm seemed to be mostly dissociated in micrograins. The ceramic grains were coated with and bonded between each other by the polymer matrix, which acted as spacer in between the ceramic grains, creating a macroporous-like material structure.

Association and Thermal Gelation in Aqueous Mixtures of Ethyl(hydroxyethyl)cellulose and Ionic Surfactant: FTIR and Raman Study

The first attempt to investigate polymer−surfactant interactions in gelling and nongelling aqueous mixtures of a nonionic cellulose ether and a surfactant by means of vibrational spectroscopy is presented. A series of aqueous solutions of ethyl(hydroxyethyl)cellulose (EHEC) with addition of anionic surfactant sodium dodecyl sulfate (SDS) of different concentrations was thoroughly investigated by means of Raman scattering and FTIR absorption techniques. Our data show that even in the sol state (i.e., below the gel point) there are interactions between the polymer and the surfactant, and both bound and free surfactant molecules were detected. This interaction, which cannot be characterized as a chemical one, occurs mainly between the side chains of the polymer and the sulfonic acid groups of SDS. Above the gel point, a new type of interaction appears, which mainly involves the SO3- groups and water molecules. The intermolecular interactions are studied vs changes of both temperature and polymer−surfactant c...

セルロースエーテルを用いたセメント系マトリクスのフレッシュ性状の材料設計法に関する基礎的研究

The nonionic cellulose ether, which is a kind of water soluble polymer, is used for several cement matrices such as plastering porlar, tile portar, self leveling materials, high fluidity concrete, antiwashout underwater concrete, c. i. c.. The purpose of this study was to clarify the influence of the molecular weight and concentration of cellulose ether on fresh properties in cement matrix containing cellulose ether. The results obtained were as follows. 1) Fresh properties (such as water retentivity, bleeding, consistency) were affected by molecular weight and concentration of cellulose ether as well as rheological property. 2) From the results on material design method, fresh properties were able to express as a function of the molecular weight of cellulose ether and the concentration.

Microviscosity in dilute aqueous solutions of SDS and non-ionic cellulose derivatives of different hydrophobicity: fluorescence probe investigations

The microviscosity in mixed micelles formed in dilute aqueous solutions of sodium dodecyl sulphate (SDS) and a set of non-ionic cellulose ethers of different hydrophobicity has been determined by means of steady-state fluorescence probe techniques. Two hydrophobic probes have been applied in this investigation: 1,3-di(1-pyrenyl)propane (P3P) and perylene. Reference measurements of microviscosity have also been performed on SDS solutions including the uncharged polymers poly(ethyleneoxide) (PEO) or poly(vinylpyrrolidone) (PVP). All compositions investigated showed qualitatively the same general behaviour with an abrupt increase in microviscosity at the critical surfactant concentration where the polymer-surfactant interaction starts ( c 1) followed by a maximum and an asymptotically declining region as the surfactant concentration was increased further. Comparison with a recent investigation of a specific ethyl(hydroxyethyl)cellulose (EHEC fraction CST-103)/ SDS/water system (Evertsson & Nilsson (1997) Macromolecules, 30, 2377) revealed that the maximum in microviscosity generally corresponds to a low degree of SDS adsorption (≈ 0.5 mmol of SDS per gram of polymer) and consequently to a high polymer content of the mixed micelles formed in the type of systems studied herein. The hydrophobicity of the cellulose derivatives was found to correlate to the amplitude of the overall microviscosity pattern for the mixed micelles, i.e. an increased polymer hydrophobicity gave an increased rigidity of the polymersurfactant aggregates. An approximately exponential relation was demonstrated between the maxima in microviscosity of the different mixed micelles and the surface activities of the corresponding cellulose derivatives. All polymer/surfactant combinations investigated gave aggregates with a higher rigidity than ordinary SDS micelles. The microviscosity of the mixed micelles of the cellulose derivatives and SDS formed close to c 1 increased as the temperature rose from 20 to 50 °C. This effect was attributed to an increased hydrophobicity of the cellulose ethers upon temperature elevation, hence giving rise to further close-packing of the aggregate structures.

Influence of Cosolutes on Phase Behavior and Viscosity of a Nonionic Cellulose Ether. The Effect of Hydrophobic Modification

The phase behavior and viscosity of aqueous solutions of two nonionic polymers, ethyl(hydroxyethyl)cellulose (EHEC) and the hydrophobically modified analogue (HM-EHEC), have been studied as a function of added cosolutes, ranging from alcohols with different chain lengths to salts with different anions and to substances usually referred to as denaturants. The change in phase behavior on addition of a cosolute is dominated by the general structure of the polymer chain and is negligibly influenced by the hydrophobic tails of HM-EHEC, as they are present in such a low number. Therefore, the cosolute induced changes in phase behavior are akin for the two polymers. However, the situation is different for added cosolutes which have a particularly strong affinity for the hydrophobic moieties of HM-EHEC and at a closer inspection differences in phase behavior between the two polymers can be seen on addition of long-chained alcohols. On the other hand, changes in viscosity on addition of cosolutes are generally much more pronounced for HM-EHEC as rheology probes network formation and association resulting from small changes in the interaction energy between the polymer chains. The observations, both phase behavior and viscosity, can be qualitatively understood in terms of the distribution of cosolute between bulk solution and polymer surface. As an example, addition of NaCl or a long-chained alcohol increases the viscosity more for HM-EHEC than for EHEC, while an addition of NaSCN or a short-chained alcohol rather decreases the viscosity, again more pronounced for HM-EHEC.

Effects of Temperature, Surfactant, and Salt on the Rheological Behavior in Semidilute Aqueous Systems of a Nonionic Cellulose Ether

Oscillatory shear experiments have been carried out on thermoreversible gelling and nongelling semidilute aqueous systems of ethyl(hydroxyethyl)cellulose (EHEC) (at a constant polymer concentration of 1 wt %) in the presence of various amounts of sodium dodecyl sulfate (SDS) and at some different levels of NaCl addition. Depending on the concentrations of surfactant and salt, a temperature-induced sol-gel transition or only a viscosification of the solution was observed. For the gelling systems, the value of the gel temperature, determined by the observation of a frequency independent loss tangent, was found to be dependent on the composition of the system. At the gel temperature, a power law frequency dependence of the dynamic storage modulus (G‘ ∼ ωn‘) and loss modulus (G‘‘ ∼ ωn‘‘) was constantly observed with n‘ = n‘‘ = n. Values of the viscoelastic exponent n in the range 0.3−0.4 were reported. The value of n, as well as the gel strength parameter S, was dependent on the composition of the system. The...

On the characterization principles of some technically important water soluble non-ionic cellulose derivatives

Principles are developed and discussed for a detailed characterization of water soluble polymers (cellulose ethers) as to hydrodynamic and thermodynamic behaviour, molecular size in solution in solvents of varying hydrophilicity and aggregation. In particular, the application of dynamic light scattering (DLS) and size exclusion chromatography is discussed and compared with static light scattering and viscometry. Results are given for eight non-ionic cellulose ether samples concerning phase separation properties, intrinsic viscosity, Huggins' constant, weight and number average molecular weight, second virial coefficient, radius of gyration, molecular weight distribution, and hydrodynamic particle size parameters from DLS. The results are also discussed in terms of chemical properties such as degree and type of substitution and cloud point. Values of refractive index increments have been measured for all samples in the two solvents used.

Rheological and dynamic light-scattering studies on aqueous solutions of a hydrophobically modified nonionic cellulose ether and its unmodified analog

Dynamic light-scattering (DLS) and oscillatory shear experiments have been carried out on aqueous solutions ofethyl(hydroxyethyl)cellulose (EHEC) and of a hydrophobically modified analogue (HM-EHEC) in the presence of various amounts of sodium dodecyl sulfate (SDS). Both the rheological and the DLS measurements revealed significant polymer-surfactant interaction for the EHEC/SDS and HM-EHEC/SDS systems at surfactant concentrations of 8-10 and 4-5 mm, respectively. The observed rheological and hydrodynamic effects for both systems were found to be strongly dependent upon the level of surfactant addition, with at first an increase and then a decrease in the values of parameters such as the dynamic viscosity, the storage and loss moduli, the slow relaxation time from DLS, and the wave vector dependence of the slow inverse relaxation time. The strength of interaction was considerably stronger in solutions of the hydrophobically modified polymer at moderate surfactant concentrations due to enhanced hydrophobic associations. At higher surfactant concentrations, a breakdown of chain associations occurred. The rheological properties of the hydrophobically modified polymer at moderate surfactant concentrations suggest that the elastic response dominates at higher frequencies. The time correlation data obtained from the DLS experiments revealed, for both systems at all surfactant concentrations, the existence of two relaxation modes, one single exponential at short times followed by a stretched exponential at longer times. The values of the slow relaxation time were constantly found to be several orders of magnitude higher than those of the fast relaxation time, with a maximum value observed for the HM-EHEC/SDS system at a surfactant concentration of about 4 mm. The fast mode was always diffusive, while the slow mode exhibited a stronger and more complex wave vector dependence. Under certain polymer-surfactant conditions, the DLS results at low scattering angles indicated the formation of large clusters.

Silylated Cellulose Materials in Design of Supramolecular Structures of Ultrathin Cellulose Films

Abstract To use the structure-forming potential and the biodegradability of cellulose and nonionic cellulose ethers, we developed synthesis pathways for soluble and regenerable silyl celluloses suitable for the design of advanced materials. A 6-0-silylation of cellulose takes place in a heterogeneous phase reaction in the presence of ammonia-saturated polar aprotic solvents at −15°C with thexyldimethylchlorosilane. After 2,3-di-O-methylation, this type of regioselectively-substituted cellulose derivatives yields sensor matrices for the detection of halohydrocarbons in air. On the other hand, thexyldimethylsilyl celluloses and trimethylsilyl celluloses with degrees of substitution in the 2.6 to 3.0 range form mono-and multilayered supramolecular structures by applying the Langmuir–Blodgett technique and, after desilylation, oriented ultrathin cellulose films.

Interactions of Ionic Surfactants with a Nonionic Cellulose Ether in Solution and in the Gel State Studied by Pulsed Field Gradient NMR

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTInteractions of Ionic Surfactants with a Nonionic Cellulose Ether in Solution and in the Gel State Studied by Pulsed Field Gradient NMRH. Walderhaug, B. Nystroem, F. K. Hansen, and B. LindmanCite this: J. Phys. Chem. 1995, 99, 13, 4672–4678Publication Date (Print):March 1, 1995Publication History Published online1 May 2002Published inissue 1 March 1995https://doi.org/10.1021/j100013a044RIGHTS & PERMISSIONSArticle Views219Altmetric-Citations44LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (939 KB) Get e-Alerts